From a growing consciousness on the environment in recent years, introduction of a generation facility using with small environmental load, particularly the generation facility using natural energy is promoted on a global basis. At present, introduction of these facilities has been promoted by overly or partially subsidized by support measures by subsidy of each country.
In order to expedite the subsidy to the generation facility with small environmental load and the generation facility by natural energy and energy saving, there is a suggestion such as collecting an environmental tax directly or indirectly to return the tax revenue newly to an environmental contribution. Therefore, the introduction of the generation facility with small environmental load would be expedited hereafter.
Meanwhile, in order to diffuse these generation facilities, by an effort such as increase of performance and reduction of cost by a company who develops, manufactures, and sells the generation facility, a price of the generation facility has been steadily reduced these years, and further by a power purchase menu at an economically profitable price and by a method such as improving economy as an overall system by using together the other energy saving equipment to assist the introduction of these generation facilities, a diffusion rate thereof has been steadily rising.
When power demand is paid more attention to, along with an improvement in convenience of various OA machineries, air conditioner facilities, and other household appliance articles, power consumption has been rising year by year, and further a load factor, which is a ratio of electric energy of a peak hour to an average electric power, has been deteriorated year by year. A deterioration of load factor involves a problem that a power company is required to maintain the generation facility for responding to peak power, and the generation facility cannot be effectively used. In addition, thermal power generation that can be easily started and stopped is mainly used as the generation facility for responding to load variation. Therefore, a discharge of CO2 is large, compared to average all power, and this is not preferable from the viewpoint of an anti-environmental aspect. Therefore, various kinds of examinations and actions are tried to level a power load.
In addition, a conventional regulation is relaxed step-by-step by means of power liberalization hereafter, and the purchase of power from not only a power company but also an independent generation trader is enabled. Therefore, it appears that there arise various needs from environmental consciousness and a change of a system. Specifically, although the generation facility can not be held, there is a need of reducing an environmental load by raising the ratio of natural energy in the energy of self use, or there is a need of introducing the use of natural energy by the generation facility with small environmental load in one way or another.
In addition, in a special case involving a power sale, such as a large-scale generation facility like a green power fund and a green power paper, there is partly a mechanism of circulating an added value related to an environmental value of natural energy.
Patent Document 1 suggests a photovoltaic power generation management server for collecting information on a power generation and a power consumption, etc, preparing useful advice information for a cost cut, and providing it for a user.    Patent Document 1: Japanese Laid-Open Patent Publication No. 2003-259551 Patent Document 2 suggests a system capable of calculating and storing a greenhouse gas discharge, from an operative situation of facilities of a customer, and displaying its discharge.    Patent Document 2: Japanese Laid-Open Patent Publication No. 2004-326375